Investigations of binary and ternary phase change alloys for future memory applications
Aachen / Publikationsserver der RWTH Aachen University (2012, 2013) [Dissertation / PhD Thesis]
Page(s): IV, 199 S. : Ill., graph. Darst.
The understanding of phase change materials is of great importance because it enables us to predict properties and tailor alloys which might be even better suitable to tackle challenges of future memory applications. Within this thesis two topics have been approached: on the one hand the understanding of the alloy In3Sb1Te2 and on the other hand the so called resistivity drift of amorphous Ge-Sn-Te phase change materials. The main topic covers an in depth discussion of the ternary alloy In3Sb1Te2. At first glance, this alloy does not fit into the established concepts of phase alloys: e.g. the existence of resonant bonding in the crystalline phase is not obvious and the number of p-electrons is very low compared to other phase change alloys. Furthermore amorphous phase change alloys with high indium content are usually not discussed in literature, an exception being the recent work by Spreafico et al. on InGeTe2. For the first time a complete description of In3Sb1Te2alloy is given in this work for the crystalline phase, amorphous phase and crystallization process. In addition comparisons are drawn to typical phase change materials like Ge2Sb2Te5/ GeTe or prototype systems like AgInTe2 and InTe. The second topic of this thesis deals with the issue of resistivity drift, i.e. the increase of resistivity of amorphous phase change alloys with aging. This drift effect greatly hampers the introduction of multilevel phase change memory devices into the market. Recently a systematic decrease of drift coefficient with stoichiometry has been observed in our group going from GeTe over Ge3Sn1Te4 to Ge2Sn2Te4. These alloys are investigated with respect to constraint theory.
- URN: urn:nbn:de:hbz:82-opus-45528
- REPORT NUMBER: RWTH-CONV-143554